From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id DBD218D0040 for ; Tue, 29 Mar 2011 06:40:08 -0400 (EDT) Received: from m2.gw.fujitsu.co.jp (unknown [10.0.50.72]) by fgwmail5.fujitsu.co.jp (Postfix) with ESMTP id CF9413EE0C0 for ; Tue, 29 Mar 2011 19:40:05 +0900 (JST) Received: from smail (m2 [127.0.0.1]) by outgoing.m2.gw.fujitsu.co.jp (Postfix) with ESMTP id B62B745DE6D for ; Tue, 29 Mar 2011 19:40:05 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (s2.gw.fujitsu.co.jp [10.0.50.92]) by m2.gw.fujitsu.co.jp (Postfix) with ESMTP id 8896045DE6A for ; Tue, 29 Mar 2011 19:40:05 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 78EF61DB8041 for ; Tue, 29 Mar 2011 19:40:05 +0900 (JST) Received: from ml14.s.css.fujitsu.com (ml14.s.css.fujitsu.com [10.240.81.134]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 35DC01DB803C for ; Tue, 29 Mar 2011 19:40:05 +0900 (JST) From: KOSAKI Motohiro Subject: [PATCH 1/4] vmscan: all_unreclaimable() use zone->all_unreclaimable as the name In-Reply-To: <20110329193953.2B7E.A69D9226@jp.fujitsu.com> References: <20110329193953.2B7E.A69D9226@jp.fujitsu.com> Message-Id: <20110329194044.2B82.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Tue, 29 Mar 2011 19:40:04 +0900 (JST) Sender: owner-linux-mm@kvack.org List-ID: To: KOSAKI Motohiro Cc: Andrey Vagin , Minchan Kim , KAMEZAWA Hiroyuki , "Luis Claudio R. Goncalves" , LKML , linux-mm , David Rientjes , Oleg Nesterov , Andrew Morton , Linus Torvalds all_unreclaimable check in direct reclaim has been introduced at 2.6.19 by following commit. 2006 Sep 25; commit 408d8544; oom: use unreclaimable info And it went through strange history. firstly, following commit broke the logic unintentionally. 2008 Apr 29; commit a41f24ea; page allocator: smarter retry of costly-order allocations Two years later, I've found obvious meaningless code fragment and restored original intention by following commit. 2010 Jun 04; commit bb21c7ce; vmscan: fix do_try_to_free_pages() return value when priority==0 But, the logic didn't works when 32bit highmem system goes hibernation and Minchan slightly changed the algorithm and fixed it . 2010 Sep 22: commit d1908362: vmscan: check all_unreclaimable in direct reclaim path But, recently, Andrey Vagin found the new corner case. Look, struct zone { .. int all_unreclaimable; .. unsigned long pages_scanned; .. } zone->all_unreclaimable and zone->pages_scanned are neigher atomic variables nor protected by lock. Therefore zones can become a state of zone->page_scanned=0 and zone->all_unreclaimable=1. In this case, current all_unreclaimable() return false even though zone->all_unreclaimabe=1. Is this ignorable minor issue? No. Unfortunatelly, x86 has very small dma zone and it become zone->all_unreclamble=1 easily. and if it become all_unreclaimable=1, it never restore all_unreclaimable=0. Why? if all_unreclaimable=1, vmscan only try DEF_PRIORITY reclaim and a-few-lru-pages>>DEF_PRIORITY always makes 0. that mean no page scan at all! Eventually, oom-killer never works on such systems. That said, we can't use zone->pages_scanned for this purpose. This patch restore all_unreclaimable() use zone->all_unreclaimable as old. and in addition, to add oom_killer_disabled check to avoid reintroduce the issue of commit d1908362. Reported-by: Andrey Vagin Cc: Nick Piggin Reviewed-by: Minchan Kim Cc: KAMEZAWA Hiroyuki Signed-off-by: KOSAKI Motohiro --- mm/vmscan.c | 24 +++++++++++++----------- 1 files changed, 13 insertions(+), 11 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index f73b865..c3c095d 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -41,6 +41,7 @@ #include #include #include +#include #include #include @@ -1988,17 +1989,12 @@ static bool zone_reclaimable(struct zone *zone) return zone->pages_scanned < zone_reclaimable_pages(zone) * 6; } -/* - * As hibernation is going on, kswapd is freezed so that it can't mark - * the zone into all_unreclaimable. It can't handle OOM during hibernation. - * So let's check zone's unreclaimable in direct reclaim as well as kswapd. - */ +/* All zones in zonelist are unreclaimable? */ static bool all_unreclaimable(struct zonelist *zonelist, struct scan_control *sc) { struct zoneref *z; struct zone *zone; - bool all_unreclaimable = true; for_each_zone_zonelist_nodemask(zone, z, zonelist, gfp_zone(sc->gfp_mask), sc->nodemask) { @@ -2006,13 +2002,11 @@ static bool all_unreclaimable(struct zonelist *zonelist, continue; if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) continue; - if (zone_reclaimable(zone)) { - all_unreclaimable = false; - break; - } + if (!zone->all_unreclaimable) + return false; } - return all_unreclaimable; + return true; } /* @@ -2108,6 +2102,14 @@ out: if (sc->nr_reclaimed) return sc->nr_reclaimed; + /* + * As hibernation is going on, kswapd is freezed so that it can't mark + * the zone into all_unreclaimable. Thus bypassing all_unreclaimable + * check. + */ + if (oom_killer_disabled) + return 0; + /* top priority shrink_zones still had more to do? don't OOM, then */ if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc)) return 1; -- 1.7.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org